<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <title>一个计数时钟</title>
</head>
<body>
<div id="output"></div>
<script>
    function updateTime() {
        document.getElementById('output').innerHTML = new Date().toTimeString();
    }
    setInterval(updateTime, 1000);
</script>
</body>
</html>